Contemporary design processes often require the rapid fabrication of prototypes and models of complex mechanical parts in low volumes and with minimum setup and fabrication times to allow the evaluation and testing of the design of such parts within very short design and development periods. Most conventional fabrication methods, however, are unsuitable for such purposes. Manual machining, for example, is sometimes suitable for relatively simple designs but is too slow and expensive for complex designs and Computer Numerically Controlled (CNC) machine processes, while suitable for complex designs, have significant limitations as regards the types or configurations of parts that can be fabricated.
The need for rapid, low cost, low volume fabrication of complex parts has generally been met by the development of various three dimensional (3D) modeling processes that employ layer by layer “printing” processes. In typical 3D modeling processes of the prior art, a part is built up by the successive deposition of layers comprising a “model” material forming the actual part and a sacrificial material that provides support for the model material during the fabrication process, with the sacrificial material being subsequently removed, during a removal process, thereby leaving the model material forming the actual part.
Examples of 3D modeling processes of the prior art are described for example, in U.S. Pat. Nos. 4,247,508, 5,136,515, 5,260,009, 5,506,607, 5,740,051, and 6,175,422. Yet other systems and methods of the prior are described, for example, in U.S. Patent Publication Nos. 2009/025282 and 2005/087897, which relate to variations of the basic method for constructing a model by deposition of successive layers of a model material. U.S. Pat. No. 5,209,878 relates to the use of either thin partial layers of material or a material capable forming a meniscus in the edge regions between successive layers of different dimensions. U.S. Patent Publication No. 2002/0129485 describes a system which is an agglomeration of previously known systems for fabricating three dimensional objects which thereby provides a very flexible, but complex system capable of achieving features of a wide variety of methods.
U.S. Pat. No. 5,121,329 relates to an apparatus incorporating a movable dispensing head driven by a computer utilizing computer aided design (CAD). The apparatus includes a protruding discharge nozzle, having a bottom surface with a flat face, for sequentially forming layers of a desired material. A supply material control is provided via constant fluid pressure of the supply material and proportionally regulating the linear speed of the drive motor in relation to the speed of the dispensing head. U.S. Pat. No. 5,340,433 is a related continuation-in-part in which the material is supplied in the form of a continuous, flexible strand or filament.
Other prior art systems employ methods somewhat analogous to those used to construct three dimensional objects as successive layers of different materials, but as adapted specifically and essentially to object molding processes. For example, U.S. Patent Publication No. 2004/0089980 describes a method for fabricating three dimensional models by deposition and machining three or four successive thick layers, thereby concurrently forming a mold for the object and the object itself.
U.S. Pat. No. 7,003,864 describes a method, that is generally similar to U.S. Patent Publication No. 2004/0089980, of depositing and machining three layers which concurrently form a mold for an object and the object itself, including depositing and planing a base layer of support material, depositing and removing regions of a second layer to form a mold of the part, adding a construction material to the removed regions of the second layer, and planing or machining the support and construction materials of the second layer.